This invention generally relates to catheters, and particularly intravascular catheters for use in percutaneous transluminal coronary angioplasty (PTCA) or for the delivery of stents.
In a typical PTCA procedure, a dilatation balloon catheter is advanced over a guidewire to a desired location within the patient's coronary anatomy, to position the balloon of the dilatation catheter within the stenosis to be dilated. The balloon is then inflated with radiopaque liquid at relatively high pressures (generally 4-16 atmospheres) to dilate the stenosed region of the diseased artery. One or more inflations may be needed to effectively dilate the stenosis. Additionally, a stent may be implanted within the artery, typically by delivery to a desired location within the artery in a contracted condition on a balloon of a catheter which is similar in many respects to a balloon angioplasty catheter and expansion to a larger diameter by inflation of the balloon.
In rapid exchange type balloon catheters, the catheter has an inflation lumen extending from the proximal end of the catheter to a balloon on a distal shaft section, a distal guidewire port at the distal end of the catheter, a proximal guidewire port located distal to the proximal end of the catheter, and a relatively short guidewire lumen extending therebetween. The distal shaft section defines the guidewire lumen, and a distal portion of the inflation lumen in fluid communication with the proximal portion of the inflation lumen defined by the single lumen proximal shaft section. The rapid exchange junction located at the proximal guidewire port at the transition between the proximal shaft section and the distal shaft section should provide a good transition in flexibility from the relatively stiff proximal shaft section to the relatively flexible distal shaft section to facilitate tracking the catheter within the patient's tortuous vasculature. One difficulty has been forming a rapid exchange junction with the desired characteristics of flexibility, kink resistance, and pushability (i.e., the ability to transmit force from the proximal end to the distal end of the catheter).
To help meet the desire for a catheter having sufficient pushability and crossability, while maintaining trackability, prior art designs have supplemented polymer catheter shafts with a support mandrel. Other prior art designs have addressed these handling and performance issues by using materials of different stiffness for the proximal and distal portions of the catheter, and employing a high strength metallic proximal shaft section, commonly called a hypotube. To prevent kinking at the junction of these two materials, while maintaining trackability and pushability, some conventional designs have employed reinforcing layers or stiffening wires to bridge the transition in catheter shaft material. Despite these attempts, prior art designs have suffered from various drawbacks relating to these handling and performance issues.
Accordingly, it would be a significant advance to provide a catheter having an improved rapid exchange junction.